Crowded optic nerve head evaluation with optical coherence tomography in anterior ischemic optic neuropathy

Purpose To characterize the optic nerve head (ONH) structure in patients with non-arteritic anterior ischemic optic neuropathy (NAION) compared to healthy control subjects using spectral domain optical coherence tomography (SD-OCT) via the enhanced depth imaging method. Methods In this prospective, cross-sectional, comparative study, we assessed 66 eyes of 33 patients with unilateral NAION and 31 eyes of 31 healthy normal subjects in an academic institution. The peripapillary nerve fiber layer thickness, disc area, and quantitative parameters of the ONH structures, including the Bruch's membrane opening (BMO) area, anterior laminar depth, and prelaminar thickness and depth were compared between the three groups. Results Linear mixed model analysis after adjusting for age, sex, and axial length showed that the BMO area was similar in eyes with NAION (1.89 +/- 0.33 mm(2)), their fellow eyes (1.8 5 +/- 0.35 mm(2)), and control eyes (1.88 +/- 0.37 mm(2); all P > 0.99). Anterior laminar depth was also similar in the three groups. The mean prelaminar tissue thickness of the NAION eyes was 445 +/- 176 mu m, which was thinner than the prelaminar tissue of their unaffected fellow eyes (mean, 539 +/- 227 mu m, P = 0.004), but both were thicker than the prelaminar tissue of the normal subjects (mean 243 +/- 145 mu m, P = 0.001 and P < 0.001, respectively). Conclusions The thick prelaminar thickness is associated with unilateral NAION in the affected and unaffected eyes.